Scripulum

The scripulum was a gold denomination introduced by Constantine, worth 1 1/2 of a solidus.


1½ Scripulum (Nine Siliquae)

"1½ Scripulum" is the modern name for the gold coin introduced by the Constantine I about 310.  Its ancient name isn't known, so it is referred to by its weight in the Roman system.  The "scripulum" was a small weight unit, being 1/24 of a Roman "uncia" (ounce).  Therefore a 1½ scripulum piece weighed 1/16 of a Roman ounce (1.71 grams).  Since the standard gold coin, the solidus, was struck at 6 to the Roman ounce, the 1½ scripulum was equal to exactly 3/8 of a solidus.  Further, since a solidus equaled 24 siliquae, the 1½ scripulum is sometimes called a "nine-siliquae" piece.  It wasn't struck after 385.

The 1½ scripulum piece was introduced at about the same time as Constantine I introduced the new Roman standard for gold coins, a standard based upon the "solidus" coin.  The solidus replaced the previous Roman standard of the "aureus" coin, which had been struck at sixty to the Roman pound or five to the Roman ounce.  The solidus was a lighter weight coin which was struck at 72 to the Roman pound or six to the Roman ounce.  The solidus was therefore equal to a "sextula" or one-sixth (1/6) of a Roman ounce.  Since the Romans had no name for a fifth of a Roman ounce (the weight of the aureus), the solidus actually conformed better to the Roman system of weights.

A 1½ scripulum seems to be an odd denomination, but since its weight was (1½ x 1/24 ounce) or 1/16th of a Roman ounce, it actually bore a relationship to the solidus.  Since the solidus was equal to 1/6 of a Roman ounce and the 1½ scripulum coin was equal to 1/16 of a Roman ounce, the 1½ scripulum coin was exactly equal to three-eighths (3/8) of a solidus.  In our modern system of weight the 1½ scripulum piece weighed a theoretical 1.71 grams.

Perhaps as early as 315 Constantine I began to produce a silver coin called a "siliqua" which was struck at the rate of 96 to the Roman pound (8 to the Roman ounce).  This coin was tariffed at 24 to the solidus (a ratio of 18:1 by weight), and hence the 1½ scripulum piece is sometimes referred to as a nine-siliquae piece (3/8 x 24 = 9).

Source: Moneta Historical Research by Thomas Schroer